/*
 * jcdctmgr.c
 *
 * Copyright (C) 1994-1995, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains the forward-DCT management logic.
 * This code selects a particular DCT implementation to be used,
 * and it performs related housekeeping chores including coefficient
 * quantization.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"        /* Private declarations for DCT subsystem */


/* Private subobject for this module */

typedef struct {
    struct jpeg_forward_dct pub;/* public fields */

    /* Pointer to the DCT routine actually in use */
    forward_DCT_method_ptr do_dct;

    /* The actual post-DCT divisors --- not identical to the quant table
     * entries, because of scaling (especially for an unnormalized DCT).
     * Each table is given in normal array order; note that this must
     * be converted from the zigzag order of the quantization tables.
     */
    DCTELEM * divisors[NUM_QUANT_TBLS];

#ifdef DCT_FLOAT_SUPPORTED
    /* Same as above for the floating-point case. */
    float_DCT_method_ptr do_float_dct;
    FAST_FLOAT *         float_divisors[NUM_QUANT_TBLS];
#endif
} my_fdct_controller;

typedef my_fdct_controller * my_fdct_ptr;


/*
 * Initialize for a processing pass.
 * Verify that all referenced Q-tables are present, and set up
 * the divisor table for each one.
 * In the current implementation, DCT of all components is done during
 * the first pass, even if only some components will be output in the
 * first scan.  Hence all components should be examined here.
 */

METHODDEF void
start_pass_fdctmgr( j_compress_ptr cinfo ) {
    my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
    int ci, qtblno, i;
    jpeg_component_info * compptr;
    JQUANT_TBL * qtbl;
    //DCTELEM * dtbl;

    for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
          ci++, compptr++ ) {
        qtblno = compptr->quant_tbl_no;
        /* Make sure specified quantization table is present */
        if ( ( qtblno < 0 ) || ( qtblno >= NUM_QUANT_TBLS ) ||
            ( cinfo->quant_tbl_ptrs[qtblno] == NULL ) ) {
            ERREXIT1( cinfo, JERR_NO_QUANT_TABLE, qtblno );
        }
        qtbl = cinfo->quant_tbl_ptrs[qtblno];
        /* Compute divisors for this quant table */
        /* We may do this more than once for same table, but it's not a big deal */
        switch ( cinfo->dct_method ) {
#ifdef DCT_ISLOW_SUPPORTED
            case JDCT_ISLOW:
                /* For LL&M IDCT method, divisors are equal to raw quantization
                 * coefficients multiplied by 8 (to counteract scaling).
                 */
                if ( fdct->divisors[qtblno] == NULL ) {
                    fdct->divisors[qtblno] = (DCTELEM *)
                                             ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                                          DCTSIZE2 * SIZEOF( DCTELEM ) );
                }
                dtbl = fdct->divisors[qtblno];
                for ( i = 0; i < DCTSIZE2; i++ ) {
                    dtbl[i] = ( (DCTELEM) qtbl->quantval[jpeg_zigzag_order[i]] ) << 3;
                }
                break;
#endif
#ifdef DCT_IFAST_SUPPORTED
            case JDCT_IFAST:
            {
                /* For AA&N IDCT method, divisors are equal to quantization
                 * coefficients scaled by scalefactor[row]*scalefactor[col], where
                 *   scalefactor[0] = 1
                 *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
                 * We apply a further scale factor of 8.
                 */
#define CONST_BITS 14
                static const INT16 aanscales[DCTSIZE2] = {
                    /* precomputed values scaled up by 14 bits: in natural order */
                    16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
                    22725, 31521, 29692, 26722, 22725, 17855, 12299,  6270,
                    21407, 29692, 27969, 25172, 21407, 16819, 11585,  5906,
                    19266, 26722, 25172, 22654, 19266, 15137, 10426,  5315,
                    16384, 22725, 21407, 19266, 16384, 12873,  8867,  4520,
                    12873, 17855, 16819, 15137, 12873, 10114,  6967,  3552,
                    8867, 12299, 11585, 10426,  8867,  6967,  4799,  2446,
                    4520,  6270,  5906,  5315,  4520,  3552,  2446,  1247
                };
                SHIFT_TEMPS

                if ( fdct->divisors[qtblno] == NULL ) {
                    fdct->divisors[qtblno] = (DCTELEM *)
                                             ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                                          DCTSIZE2 * SIZEOF( DCTELEM ) );
                }
                dtbl = fdct->divisors[qtblno];
                for ( i = 0; i < DCTSIZE2; i++ ) {
                    dtbl[i] = (DCTELEM)
                              DESCALE( MULTIPLY16V16( (INT32) qtbl->quantval[jpeg_zigzag_order[i]],
                                                     (INT32) aanscales[i] ),
                                       CONST_BITS - 3 );
                }
            }
                break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
            case JDCT_FLOAT:
            {
                /* For float AA&N IDCT method, divisors are equal to quantization
                 * coefficients scaled by scalefactor[row]*scalefactor[col], where
                 *   scalefactor[0] = 1
                 *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
                 * We apply a further scale factor of 8.
                 * What's actually stored is 1/divisor so that the inner loop can
                 * use a multiplication rather than a division.
                 */
                FAST_FLOAT * fdtbl;
                int row, col;
                static const double aanscalefactor[DCTSIZE] = {
                    1.0, 1.387039845, 1.306562965, 1.175875602,
                    1.0, 0.785694958, 0.541196100, 0.275899379
                };

                if ( fdct->float_divisors[qtblno] == NULL ) {
                    fdct->float_divisors[qtblno] = (FAST_FLOAT *)
                                                   ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                                                DCTSIZE2 * SIZEOF( FAST_FLOAT ) );
                }
                fdtbl = fdct->float_divisors[qtblno];
                i = 0;
                for ( row = 0; row < DCTSIZE; row++ ) {
                    for ( col = 0; col < DCTSIZE; col++ ) {
                        fdtbl[i] = (FAST_FLOAT)
                                   ( 1.0 / ( ( (double) qtbl->quantval[jpeg_zigzag_order[i]] *
                                              aanscalefactor[row] * aanscalefactor[col] * 8.0 ) ) );
                        i++;
                    }
                }
            }
                break;
#endif
            default:
                ERREXIT( cinfo, JERR_NOT_COMPILED );
                break;
        }
    }
}


/*
 * Perform forward DCT on one or more blocks of a component.
 *
 * The input samples are taken from the sample_data[] array starting at
 * position start_row/start_col, and moving to the right for any additional
 * blocks. The quantized coefficients are returned in coef_blocks[].
 */

METHODDEF void
forward_DCT( j_compress_ptr cinfo, jpeg_component_info * compptr,
             JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
             JDIMENSION start_row, JDIMENSION start_col,
             JDIMENSION num_blocks ) {
/* This version is used for integer DCT implementations. */
/* This routine is heavily used, so it's worth coding it tightly. */
    my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
    forward_DCT_method_ptr do_dct = fdct->do_dct;
    DCTELEM * divisors = fdct->divisors[compptr->quant_tbl_no];
    DCTELEM workspace[DCTSIZE2];/* work area for FDCT subroutine */
    JDIMENSION bi;

    sample_data += start_row;/* fold in the vertical offset once */

    for ( bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE ) {
        /* Load data into workspace, applying unsigned->signed conversion */
        { register DCTELEM * workspaceptr;
          register JSAMPROW elemptr;
          register int elemr;

          workspaceptr = workspace;
          for ( elemr = 0; elemr < DCTSIZE; elemr++ ) {
              elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8        /* unroll the inner loop */
              *workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
              *workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
              *workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
              *workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
              *workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
              *workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
              *workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
              *workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
#else
              { register int elemc;
            for ( elemc = DCTSIZE; elemc > 0; elemc-- ) {
                *workspaceptr++ = GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE;
            }
              }
#endif
          }
        }

        /* Perform the DCT */
        ( *do_dct )( workspace );

        /* Quantize/descale the coefficients, and store into coef_blocks[] */
        { register DCTELEM temp, qval;
          register int i;
          register JCOEFPTR output_ptr = coef_blocks[bi];

          for ( i = 0; i < DCTSIZE2; i++ ) {
              qval = divisors[i];
              temp = workspace[i];
              /* Divide the coefficient value by qval, ensuring proper rounding.
               * Since C does not specify the direction of rounding for negative
               * quotients, we have to force the dividend positive for portability.
               *
               * In most files, at least half of the output values will be zero
               * (at default quantization settings, more like three-quarters...)
               * so we should ensure that this case is fast.  On many machines,
               * a comparison is enough cheaper than a divide to make a special test
               * a win.  Since both inputs will be nonnegative, we need only test
               * for a < b to discover whether a/b is 0.
               * If your machine's division is fast enough, define FAST_DIVIDE.
               */
#ifdef FAST_DIVIDE
#define DIVIDE_BY( a, b )  a /= b
#else
#define DIVIDE_BY(a,b)	if (a >= b) a /= b; else a = 0
#endif
              if ( temp < 0 ) {
                  temp = -temp;
                  temp += qval >> 1;/* for rounding */
                  DIVIDE_BY( temp, qval );
                  temp = -temp;
              } else {
                  temp += qval >> 1;/* for rounding */
                  DIVIDE_BY( temp, qval );
              }
              output_ptr[i] = (JCOEF) temp;
          }
        }
    }
}


#ifdef DCT_FLOAT_SUPPORTED

METHODDEF void
forward_DCT_float( j_compress_ptr cinfo, jpeg_component_info * compptr,
                   JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
                   JDIMENSION start_row, JDIMENSION start_col,
                   JDIMENSION num_blocks ) {
/* This version is used for floating-point DCT implementations. */
/* This routine is heavily used, so it's worth coding it tightly. */
    my_fdct_ptr fdct = (my_fdct_ptr) cinfo->fdct;
    float_DCT_method_ptr do_dct = fdct->do_float_dct;
    FAST_FLOAT * divisors = fdct->float_divisors[compptr->quant_tbl_no];
    FAST_FLOAT workspace[DCTSIZE2];/* work area for FDCT subroutine */
    JDIMENSION bi;

    sample_data += start_row;/* fold in the vertical offset once */

    for ( bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE ) {
        /* Load data into workspace, applying unsigned->signed conversion */
        { register FAST_FLOAT * workspaceptr;
          register JSAMPROW elemptr;
          register int elemr;

          workspaceptr = workspace;
          for ( elemr = 0; elemr < DCTSIZE; elemr++ ) {
              elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8        /* unroll the inner loop */
              *workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
              *workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
              *workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
              *workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
              *workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
              *workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
              *workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
              *workspaceptr++ = (FAST_FLOAT)( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
#else
              { register int elemc;
            for ( elemc = DCTSIZE; elemc > 0; elemc-- ) {
                *workspaceptr++ = (FAST_FLOAT)
                                  ( GETJSAMPLE( *elemptr++ ) - CENTERJSAMPLE );
            }
              }
#endif
          }
        }

        /* Perform the DCT */
        ( *do_dct )( workspace );

        /* Quantize/descale the coefficients, and store into coef_blocks[] */
        { register FAST_FLOAT temp;
          register int i;
          register JCOEFPTR output_ptr = coef_blocks[bi];

          for ( i = 0; i < DCTSIZE2; i++ ) {
              /* Apply the quantization and scaling factor */
              temp = workspace[i] * divisors[i];
              /* Round to nearest integer.
               * Since C does not specify the direction of rounding for negative
               * quotients, we have to force the dividend positive for portability.
               * The maximum coefficient size is +-16K (for 12-bit data), so this
               * code should work for either 16-bit or 32-bit ints.
               */
              output_ptr[i] = (JCOEF) ( (int) ( temp + (FAST_FLOAT) 16384.5 ) - 16384 );
          }
        }
    }
}

#endif /* DCT_FLOAT_SUPPORTED */


/*
 * Initialize FDCT manager.
 */

GLOBAL void
jinit_forward_dct( j_compress_ptr cinfo ) {
    my_fdct_ptr fdct;
    int i;

    fdct = (my_fdct_ptr)
           ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                        SIZEOF( my_fdct_controller ) );
    cinfo->fdct = (struct jpeg_forward_dct *) fdct;
    fdct->pub.start_pass = start_pass_fdctmgr;

    switch ( cinfo->dct_method ) {
#ifdef DCT_ISLOW_SUPPORTED
        case JDCT_ISLOW:
            fdct->pub.forward_DCT = forward_DCT;
            fdct->do_dct = jpeg_fdct_islow;
            break;
#endif
#ifdef DCT_IFAST_SUPPORTED
        case JDCT_IFAST:
            fdct->pub.forward_DCT = forward_DCT;
            fdct->do_dct = jpeg_fdct_ifast;
            break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
        case JDCT_FLOAT:
            fdct->pub.forward_DCT = forward_DCT_float;
            fdct->do_float_dct = jpeg_fdct_float;
            break;
#endif
        default:
            ERREXIT( cinfo, JERR_NOT_COMPILED );
            break;
    }

    /* Mark divisor tables unallocated */
    for ( i = 0; i < NUM_QUANT_TBLS; i++ ) {
        fdct->divisors[i] = NULL;
#ifdef DCT_FLOAT_SUPPORTED
        fdct->float_divisors[i] = NULL;
#endif
    }
}
